Still, seemingly harmless. But that little mistake later exploded into a much bigger problem: A 10-2 loss Tuesday to the Toronto Blue Jays, a team the Mariners are chasing for a playoff spot.

The next eight Blue Jays reached base after Iannetta’s error, and when the inning was done, Toronto had a commanding hold on the outcome.

“You never want to give a team extra outs, especially a team that swings the bat like that,” manager Scott Servais said. “We gave them an extra out that inning, and most times it will come back to haunt you.”

The Mariners (79-72) have now lost four of their past five games — all at home, all against teams in the playoff hunt. They’ve squandered the momentum and goodwill they’d acquired with their eight-game winning streak.

When the Mariners headed home on Sept. 14 last week, they trailed the second wild-card spot by 1½ games. After the loss to the Blue Jays, the Mariners are three games out with 11 games left. The loss stings even more because the Orioles, the team holding the second wild-card spot, lost.

“We’re just not playing good baseball,” Servais said. “That’s kind of been the story of our season. We’re really, really good or we have some ugly nights. We need to get back to doing what we do.”

The Blue Jays scored eight runs after Iannetta’s gaffe. Mariners starter Hisashi Iwakuma didn’t make it out of the inning. The Blue Jays fans among the 33,573 people in attendance filled Safeco Field with noise.

It might be putting too much on just one play, but what if Iannetta makes the play? That’s both the great and frustrating thing about baseball. Events happen (or don’t happen), and only later does the sequence have any meaning.

“The game is very fickle,” Servais said. “When you’ve got a good team down, you’ve got to finish.”

What we do know is that had Iannetta caught that foul ball, Iwakuma would have had two outs. To that point, he had allowed just two singles and had escaped his only jam. By the time the inning was over, the Blue Jays led 8-2.

That was plenty of cushion for Blue Jays pitcher and former Mariner J.A. Happ. Happ pitched five scoreless innings, striking out eight and becoming the second pitcher in the majors to pick up his 20th win of the season.

“We’ve got work to do,” Servais said. “It’s not going to be easy. And I don’t think anybody three weeks ago thought this was going to be easy, but all the sudden we made it interesting. Unfortunately, we just didn’t carry the momentum over here to the homestand.”